OK, I am now considering to create a new chain and switch over to that
as soon as possible (i.e. in RMSoapInterceptor as mentioned earlier).
Partly because I need have to ensure that the interceptors appropriate
for the parameter style used in the binding for the RM procol messages
are used. Initially this style was wrapped, but I am now changing this
to BARE (which is what you would get from using the wsdl I mailed around
earlier). Whichever style is chosen, there are problems when the
application endpoint uses the other style of binding (that is why the
RMInInterceptor removed the WrapperClassInInterceptor), and the two
solutions are to either replace the (frontend-independent)
Wrapped[In/Out]Interceptor on the chain with Bare[In/Out]Interceptor, or
to use a new chain containing interceptors chosen specifically for the
RM endpoint.
Nevertheless, the core - interceptors as well as other parts - should be
more robust, as e.g. I just found out that decoupled responses actually
don't work with bare bindings
https://issues.apache.org/jira/browse/CXF-357
I am not sure which is the better way to work around this:
Should the BareInInterceptor only do a message.setContent(List.class,
parameters);
if any parameters were found, or should the isPartialResponse check in
ClientImpl be changed to
... if (message.getContent(List.class) == null ||
message.getContent(List.class).size() == 0 || ...)?
Any opinions?
Andrea.
Dan Diephouse wrote:
this is very dangerous and way too common of a problem to rely on
catching
exceptions that might occur during processing. Making interceptors more
fault tolerant this way complicates development for advanced users,
integrators, etc. Lets say I as a user write an interceptor which
verifies
that an authentication header is present and throws a fault if it is not
present. I now need to add logic now to look for WS-* messages.
Also, it is dangerous because I think it could give into situations
where it
isn't clear if we should throw an error or if we should be catching
it. What
if the incoming message is formatted wrong and that is what throws the
ClassCastException? Now our fault tolerance has turned into fault
swallowing.
I would much prefer a more sophisticated dispatching maechanism. Here's a
look at our incoming interceptor flow with RM and Addressing enabled:
receive [AttachmentInInterceptor, InMessageRecorder]
pre-stream []
user-stream [StreamHandlerInterceptor]
post-stream [StaxInInterceptor]
read [ReadHeadersInterceptor]
pre-protocol [MustUnderstandInterceptor, MAPCodec,
SOAPHandlerInterceptor,
RMSoapInterceptor]
user-protocol []
post-protocol []
unmarshal [URIMappingInterceptor, WrappedInInterceptor,
SoapHeaderInterceptor]
pre-logical [OutgoingChainSetupInterceptor, RMInInterceptor,
MAPAggregator]
user-logical [LogicalHandlerInterceptor]
post-logical []
pre-invoke []
invoke [ServiceInvokerInterceptor]
post-invoke [OutgoingChainInterceptor]
We can recognize that a message isn't destined to the original
endpoint (and
is destined to RM) after we've parsed the headers for the most part. I
think
it is at this point that we should be re-dispatching off to the RM
service
or wherever it needs to go (by redispatching I mean creating a new chain
with the actual service's interceptors and starting it at the current
phase). Since interceptors at the beginning of the chain work with the
message itself and shouldn't make assumptions about what Service is being
invoked for the most part, this is a good breaking point to re- dispatch.
Another option to handle these scenarios would be to implement a more
advanced dispatching mechansim which dispatches to the service later
in the
chain and not at the front. I outlined some ways to do this in [1].
One of
the ways involves creating a MessageObserver for the soap binding itself.
The soap binding would then contain some logic on how to find the correct
service given the URL/soap version/etc. In theory the RM layer could then
override/preempt this logic at some point in the chain.
I'm not sure if I prefer the redispatching or the delaying Service
resolution, but I don't think I'm cool with just doing a
catch(ClassCastException).
- Dan
1.
http://mail-archives.apache.org/mod_mbox/incubator-cxf-dev/200612.mbox/[EMAIL PROTECTED]
On 1/5/07, Glynn, Eoghan <[EMAIL PROTECTED]> wrote:
> -----Original Message-----
> From: Andrea Smyth [mailto:[EMAIL PROTECTED]
> Sent: 05 January 2007 15:59
> To: [email protected]
> Subject: Re: JaxwsInterceptorRemoverInterceptor and RM
>
> >>Can you elaborate on how exactly you see this thing working?
> >>
> >>
> >
> >Well I was thinking of something even more simple ... the
> interceptors
> >should be coded defensively to "expect the unexpected" and
> simply step
> >out of the way when that occurs ... e.g. instead of the
> >HolderOutInterceptor just doing a straight cast of the
> message parts to
> >Holder and barfing with ClassCastException on any other
> type, it would
> >first check with instanceof to ensure the cast succeeds and
> otherwise
> >bail out from handleMessage() immediately.
> >
> >
> I'd be very much in favour of this - hence my question: Is it
> OK to make the HolderInInterceptor robust by performing a
> type check before casting to Holder? Or is there a more
> efficient way, e.g. check the parameter type for INOUT first,
> and only then attempt the cast?
>
> Andrea.
Well if you're worried about the runtime cost of doing the instanceof
check for every single message dispatch, then we could make an
assumption that in practice out-of-band RM protocol messages will
generally only constitute a small minority of the messages dispatched
(assuming RM sequences have a reasonable lifespan).
If this assumption holds, we could dispense with the instanceof check
and instead do the Holder cast inside a try ... catch
(ClassCastException) block, bailing out of handleMessage() in the catch
block. That way we'd take the performance hit of throwing and catching
the ClassCastException only when an RM protocol message is actually
being dispatched (presumably relatively rare) and incurr no extra cost
in the normal case.
/Eoghan
